PALSUN Technical Guide

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PALSUNTechnical ManualPE Masking: When preparing for bending of regularly cladded sheets- peel off the masking on both sides ofthe sheet along the bend line for about 100 mm (4 in) on each side in TF prepared sheets. It is possible toprocess the sheet with the masking on, up to 5 mm (0.2 in) thickness. For sheets of 6 mm thickness or morethe PE masking should be removed along the bending line, as described above. Always test a few samplesbefore proceeding to production.Heaters: Linear IR (Infrared) or resistance wires strip heating elements are used, preferably with heat reflectors.The width of the heated zone depends on the number of elements used, the spacing between them theirspecific thermal output and the distance from the target sheet.Bending process: When the sheet has reached the required temperature the heaters are to be switched off.The sheet, held in pivoted clamps, preferably equipped with a caliper, is then bent to the required angle andsecured there until it cools down and sets.Note: It is recommended to perform the bend a few degrees tighter than the required angle, as it may “goback” a little after cooling down. The desired angle may be reached after a few trials.Cooling is to be done in ambient air, taking care to avoid sudden drafts. These can cause distortion of thefinal product.Minimal Hot-Line Bending Radius is 3 times the thickness of the bent sheet. Larger radii can be achievedby widening the heated zone.C. Notes for Consideration:Local hot line bending (or any other localized heating, for the matter) induces internal stresses in the finishedpart, reducing the chemical resistance of the element at the bending line zone. Such treatment is thereforerecommended for use in less demanding environments.Localized heating and cooling expansion/contraction characteristics are unpredictable in many cases. Shortelements (up to 1.00 m or 3.0 ft) usually stay straight enough. Longer elements may distort to a concave shape(the outer edges are longer than the line-bent side due to uneven contraction).This phenomenon can be corrected or reduced by simple jigs or frames, which hold the part in the right positionduring the cooling period. Annealing (see special paragraph) may also correct this problem.It is always advised to fabricate experimental test samples to check feasibility of the bending operation.3. Drape Forming:a. Description:A simple technique, using a single positive (male) or negative (female) mold, on which a heated PALSUN sheetis placed. The sheet, softened by appropriate thermal processing, sags and conforms to the shape of the moldunder its own weight, or by slight mechanical pressure applied by hand. Drape forming is generally used toachieve simple, uniaxial, large curvature thermal forming.b. The ProcessTwo main techniques, differing by the position of the mold during the first stage.1) 1st Method: The sheet (without masking) is placed on top of the mold in its basic, flat state. Both sheetand mold are then slid into a hot-air circulating oven and heated to about 150-155?C (300-312?F). When thesheet (and mold) reaches the required temperature it sags and drapes over the heated mold. Both are thenpulled out of the oven and quickly helped, by gloved hands, to conform more precisely to the mold. It is thenallowed to cool down.28
PALSUNTechnical Manual2) 2nd Method: The sheet is placed into a hot-air circulating oven (without masking), and heated to about150-155 °C (300-312 °F). When the sheet reaches the required temperature it is quickly pulled out of theoven and placed on top of the mold. there the sheet sags, aided quickly by the gloved helping hands, andtakes the accurate shape of the mold. For better results we recommend pre-heating the mold to about 80 -100 °C (175 -210 °F) before putting the heated sheet on top. Then it is, likewise, allowed to cool down.c. Vacuum Assisted Drape Forming: The technique can be assisted by vacuum and is then very similar indetail to the male (positive) straight vacuum forming.Figure 16: Vacuum Assisted Drape FormingA. Clamped, heated PALSUN sheet can bepulled over the mold, or the mold can beforced into the sheet.HeaterB. Once the sheet has formed a seal aroundthe mold, a vacuum is drawn to pull thesheet tightly against the mold surface.C. Final wall thickness distributionin the molded part.MoldClampPALSUN SheetMoldVacuumSealThickest AreasThin AreasSealFormedPartVacuumVacuumd. Notes for Consideration: (These notes exclude the vacuum assisted drape forming).1) There is no need for pre-drying in this technique, due to the lower operating temperature it requires.2) The lower operating temperature leaves the exterior surface harder, helping to keep it mar free, with betteroptical quality.3) The emphasis on quick operation during the final finishing touch to the heated sheet derives from the rapidcooling and setting properties of the PALSUN sheet once taken out of the oven.e. The Molds:1) Regular molds can be made of metal (steel, aluminum or other) or wood, as long as it can stand thetemperature inside the oven without visible distortion. The upper surface is usually covered by heat resistantfelt, which will not mar the exterior sheet surface facing the mold face.2) Premium molds: Finished products requiring premium optical quality (like visors, police shields, vehiclessafety glazing etc.) need molds with very smooth, glossy, heat resistant upper surface. They can be made ofpolished steel, aluminum, glazed ceramics or glass.29
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Page 8 and 9: PALSUNTechnical ManualSolar Irradia
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Page 16 and 17: PALSUNTechnical Manual2. Band Saw:B
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Page 26 and 27: PALSUNTechnical ManualB. Thermoform
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PALSUN Technical Guide

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